JPS62162646A - Production of glass fine particle deposit - Google Patents

Abstract

PURPOSE:In the process where glass fine particles are deposited on a cylindrical or tubular material on its outer surface, the material is always kept clean with a gas on its surface to produce the title deposit free from contaminants and bubbles. CONSTITUTION:Glass fine particles formed by burner 12 are deposited on the outer surface of a rod 11 which is being lifted, as it is rotated, and the undeposited particles are exhausted out of the tube 14 to form a deposit 13 of glass particles. At this time,the part of the rod for the glass particles to be deposited is covered with a muffle 18 for purging and a clean gas 17 for purging is fed from the inlet 19 to keep the surface of the part 16 always clean. Thus, in the following steps, the bubbling on the boundary surfaces can be avoided in the heat treatment in a high-temperature oven and contamination can also be inhibited.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for forming an aggregate of glass particles on the outer periphery of a cylindrical or cylindrical starting material, particularly for optical fiber matrices that require high purity. The present invention relates to a method for forming a glass particle aggregate deposited on the outer periphery of a starting material, which is suitably used as an intermediate product in the production of a starting material.

[Conventional technology]

Conventionally, as a method for manufacturing quartz-based glass tubes or optical fiber base materials, there is a so-called external method as disclosed in Japanese Patent Laid-Open No. 48-73522.

This method uses rotating carbon or quartz glass,
S10. produced on the outer periphery of a refractory starting material such as alumina by a hydrolysis reaction of a glass raw material. After a predetermined amount of glass has been deposited, the deposition is stopped, the starting material is pulled out, a pipe-shaped glass aggregate is formed, and this pipe-shaped glass aggregate is sintered in a high-temperature electric furnace to make it transparent. It is vitrified to obtain pipe-shaped glass. Alternatively, in a similar manner, a solid glass base material for optical fiber is used as a starting material to form a composite of the starting material and the glass fine particle deposit formed on its outer periphery, and then the composite is formed without pulling out the starting material. It is also conceivable to further form a transparent glass layer on the outer periphery of the starting glass base material for optical fiber by heat-treating it in a high-temperature furnace and sintering the part of the glass particle deposit.

[Problems to be solved by the present invention]

In the above method, conventionally, as shown in FIG. 2, one or more burners 12 for producing glass particles are used to synthesize a glass particle deposit 13. Generally, a fuel gas (H, OH2, O, H, etc.) and an auxiliary combustion gas (01, air, etc.) are supplied to the burner 12, and a flame 21 is formed. As a glass raw material in this flame, S i04
, Gf301a, etc. are supplied, and glass fine particles Sin, , Gem, etc. are generated by a flame hydrolysis reaction. By depositing the glass particles on the outer periphery of the rotating starting material 11, a glass particle deposit 13 is formed.

The deposited body 13 is heat-treated in a high-temperature furnace to obtain a transparent glass body.

In this method, after heat treatment in a high temperature furnace, the starting material 11
In some cases, bubbles are generated at the interface with the glass body formed on the outer periphery, which is a major problem. It is impossible to remove the bubbles generated during transparent vitrification, and the area where the bubbles occur cannot be used as a good glass body. The present invention has been made to solve the above manufacturing problems.0 [Means for solving the problems] The above starting material and a glass body formed on the outer peripheral part of the starting material. As a result of various studies conducted by the present inventors regarding air bubbles generated on the interface of found. That is, as shown in FIG. 3, the glass fine particle deposit 13 is usually manufactured in a container 15 called a matsufuru, but the glass fine particles synthesized by the burner 12 are placed on the outer periphery of the starting material 11 which is pulled up while rotating. When producing the glass particle deposit body 13 by depositing, the glass particles that have not adhered are removed from the exhaust pipe 14.
The air is exhausted to the outside of the Matsufuru 15 through the air. However,
The flow of gas inside the Matsufuru 15 is complicated, and some of the particles that do not adhere to the glass fine particle deposit body 13 are not absorbed into the exhaust pipe 14 as they are, but convect within the Matsufuru 15. For this reason, the convecting fine particles are
However, some of the glass particles convecting in the region below the glass particle deposition surface include starting materials 16 that have not yet formed the glass particle deposit 13.
There are things that adhere to the surface. Also, Matsuful 15
Due to the convection of the gas formed inside, there is an increased chance that dust and the like will adhere to the surface of the starting material 11. Although the glass particles attached to the starting material 16 before forming the glass particle deposit 13 have the same composition as the particles to be deposited afterwards, their adhesion state is different, resulting in a singular point in the hardness of the deposit. , which causes bubbles during heat treatment in a high-temperature furnace. Further, other dust and the like cause not only air bubbles but also impurities in the glass, which causes light transmission loss when an optical fiber is manufactured using this glass body.

Based on extensive knowledge, a glass particle deposit is produced while purging the surface of the starting material with clean gas in order to prevent glass particles or dust from adhering to the starting material.

That is, the present invention provides a process in which a substantially cylindrical or cylindrical starting material, which is rotating with its own axis as the rotational axis, is injected into the flame of a burner for synthesizing glass particles from near one end onto the outer periphery of the starting material. The glass particles generated by supplying the glass raw material are started to be deposited, and the burner is moved relatively parallel to the axis of the starting material, thereby depositing the glass particles on the outer periphery of the starting material. This is a method of manufacturing a glass particle deposit body in which the outer circumferential surface of the starting material is always kept in a clean gas atmosphere before the glass particles are deposited in the method of forming the glass particle deposit body in the axial direction. Particularly preferred embodiments of the present invention include the above-mentioned method in which the starting material is covered with matzuru and clean gas is flowed from the lower end of the covering for purging, and one or more of the starting materials are provided at a position corresponding to the starting material at the lower part of the burner for synthesizing glass fine particles. The above-mentioned method includes purging the surface of the starting material by flowing clean gas through a purge gas introduction pipe having a gas blowing opening.

Hereinafter, the present invention will be described in detail based on Examples. The configuration of the present invention is shown in FIG. The glass fine particles generated by the glass fine particle synthesis burner 12 are attached to the outer periphery of the starting material 11 which is rotated and pulled up in the Matsufuru 15, and the glass fine particles that are not attached are left in the exhaust pipe 1.
In the method of forming the glass particulate deposit body 13 by exhausting the air, the part 16 of the starting material on which the glass particulates are to be continuously deposited is covered with a purge Matsufuru 18, and the gas is evacuated from the clean gas supply port 19 located at the lower part of the purge Matsufuru 18. By supplying clean gas (purge gas) 17,
The structure is such that the surface of the starting material 16 can be constantly purged. The purging gas used in the present invention may be any gas that does not affect the flame 21 formed by the glass particle synthesis burner 12, such as
A gas such as e is used. Furthermore, since these gases are originally used for the purpose of keeping the surface of the starting material 16 clean, they must be free of impurities, and a filter or the like for removing impurities may be attached as necessary. Also, depending on how the purge gas flows, the starting material may be cooled, which may have a negative effect on the bulk density of the glass particles deposited near the starting material. [Example 1] A glass particle deposit was synthesized in the configuration shown in FIG. 1. For purging Matsufuru, the outer diameter t of the starting material is
A glass pipe with an inner diameter of 5 times was used, and the upper end of the pipe was set at a distance of 501111 mm from the lower end of the deposition surface so as not to disturb the flame formed by the burner for synthesizing glass particles. N was used as the purge gas, and was supplied from the supply port at the lower end of the purging matsufuru through Teflon piping. A flow rate of 1517 m was adopted in consideration of flame turbulence and the cross-sectional area of the gas flow path in the purging matsuffle.

As a result, the glass particle deposit could be manufactured in the same manner as conventional methods, and no bubbles were observed to form at the interface during the heat treatment in the high-temperature furnace.

In the explanation of the present invention, based on the examples, a method was adopted in which a purging matuffle was installed around the outer periphery of the starting material and a purge gas was flowed through it to keep the outer surface of the starting material clean. The same effect can be obtained even without using a mechanism that constantly blows clean gas onto the surface of the starting material as shown in FIG. In FIG. 3, reference numeral 31 denotes a purge gas introduction pipe provided at the bottom of the Matsufuru 15, which has one or more gas blowing phase openings 52 at its tip in a portion corresponding to the starting material 16.

[Effects of the present invention]

By constantly maintaining the surface of the starting material in a clean gas atmosphere, it is possible to eliminate interfacial bubbles during the heat treatment in a high-temperature furnace in the next step, and to prevent the contamination of impurities.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams schematically explaining embodiments of the present invention. FIG. 1 is an example using a purge matzuru,
The figure shows an example using a purge gas blowing mechanism.

Claims (3)

[Claims] (1) From near one end of a substantially cylindrical or cylindrical starting material that is rotating about its own axis, a glass raw material is introduced into the flame of a burner for synthesizing glass fine particles onto the outer periphery of the starting material. By starting to deposit the glass fine particles generated by supplying the material and moving the burner relatively parallel to the axis of the starting material, a deposited body of glass fine particles is formed on the outer periphery of the starting material in the axial direction. A method for producing a glass particle deposit, characterized in that the outer peripheral surface of the starting material is always kept in a clean gas atmosphere before the glass particles are deposited. (2) The method for manufacturing a glass fine particle deposit according to claim (1), wherein the starting material is covered with a cylindrical matzuru, and the outer circumferential surface of the starting material is purged by flowing clean gas from the lower end of the matzuru. . (3) A claim that purifies the outer circumferential surface of the starting material by flowing clean gas through a purge gas introduction pipe having one or more gas blowing openings provided at a position corresponding to the starting material at the lower part of the burner for glass particle synthesis. The method for producing a glass particle deposit according to item (1).